This invention relates to a mask for X-ray lithography, and in particular to a structure of a mask having a complex pattern for preparing large scale integrated circuits.
A recent method for preparing an X-ray mask for printing lines of less than 20 A in thickness was disclosed in Fine-Line Lithography Nears Its Day in Electronics, Oct. 11, 1979 at pages 92-93. The X-ray mask suggested therein is formed by deposition at an oblique angle or shadowing of X-ray absorbent material onto relief structures having triangular or square cross-sections. The relief structure is a polyimide membrane. It is replicated by an X-ray or electron beam source onto a structure.
The X-ray masks disclosed to date have a linear pattern which can produce lines of a thickness of 20 A. However, these X-ray masks are restricted only to linear patterns in a single direction. Such masks are not completely satisfactory for use when a mask having a complex pattern is required, for example, in a mask for preparing a large scale integrated circuit ("LSI").
Accordingly, it is desirable to provide an improved fine-line X-ray lithography mask suitable for LSI.